Showing papers on "Lens (optics) published in 2000"

Negative Refraction Makes a Perfect Lens

Abstract: Optical lenses have for centuries been one of scientists’ prime tools. Their operation is well understood on the basis of classical optics: curved surfaces focus light by virtue of the refractive index contrast. Equally their limitations are dictated by wave optics: no lens can focus light onto an area smaller than a square wavelength. What is there new to say other than to polish the lens more perfectly and to invent slightly better dielectrics? In this Letter I want to challenge the traditional limitation on lens performance and propose a class of “superlenses,” and to suggest a practical scheme for implementing such a lens. Let us look more closely at the reasons for limitation in performance. Consider an infinitesimal dipole of frequency v in front of a lens. The electric component of the field will be given by some 2D Fourier expansion,

Foldable lens delivery system

Abstract: An automatic lens delivery device using a linear actuator which is specially adapted for low torque, low heat applications, and can be used to insert a lens into a user's eye. The linear actuator uses two semiconductor devices which are moved one relative to the other. The movable device pushes a push rod that delivers a lens.

Optics of the Human Eye

Abstract: The first stage in the process of vision is the formation of images of the outside world on the retina at the back of the eye This article describes the optical structure and optical properties of the human eye, how the retinal image is formed and the factors affecting its quality Brief mention is given to neural factors that combine with the optics to determine how well we see The article concentrates on the optics of healthy eyes

LED collimation optics with improved performance and reduced size

Abstract: An LED module that includes an LED (light-emitting diode) and a rotationally symmetrical, bowl-shaped collimator lens is provided. The collimator lens has an inner refractive wall, an outer reflective wall, a first surface having an entrance aperture with a recess in which the LED is situated and which collimator lens is also provided with a second surface from which light generated by the LED emerges, the normal to the surface extending substantially parallel to the axis of symmetry of the lens, and the LED module also includes one or more of the following structures: (1) a conic wall portion of the recess of the inner refractive wall at the entrance aperture that includes a curved portion, and an outer reflective wall so configured in accordance with the structure of the inner refractive wall to achieve substantial collimation of a source of light at the entrance aperture; and/or (2) a first surface of the lens that is recessed away from the LED source; and/or (3) two surfaces of said refractive wall between which the refractive function of said refractive wall is divided. The LED module offers an improvement in the performance of the Flat top Tulip Collimator disclosed and claimed in our co-pending application Ser. No. 09/415,833 in terms of reduced size, beam divergence, beam uniformity, and to some degree efficiency. Moreover, it allows a wider variety of choices in optimizing various performance characteristics, and this in turn allows more flexibility in the structure design.

The ageing lens.

Abstract: The human lens grows by a process of epithelial cell division at its equator and the formation of generations of differentiated fibre cells. Despite the process of continuous remodelling necessary to achieve growth within a closed system, the lens can retain a high level of light transmission throughout the lifetime of the individual, with the ability to form sharp images on the retina. Continuous growth of the lens solves the problem imposed by terminal differentiation within a closed, avascular system, from which cells cannot be shed. The lens fibre tips arch over the equator to meet anteriorly and posteriorly and form branching sutures of increasing complexity. The stages of branching may create the optical zones of discontinuity seen on biomicroscopy. The lens is exposed to the cumulative effects of radiation, oxidation and postranslational modification. These later proteins and other lens molecules in such a way as to impair membrane functions and perturb protein (particularly crystallin) organisation, so that light transmission and image formation may be compromised. Damage is minimised by the presence of powerful scavenger and chaperone molecules. Progressive insolublisation of the crystallins of the lens nucleus in the first five decades of life, and the formation of higher molecular weight aggregates, may account for the decreased deformability of the lens nucleus which characterises presbyopia. Additional factors include: the progressive increase in lens mass with age, changes in the point of insertion of the lens zonules, and a shortening of the radius of curvature of the anterior surface of the lens. Also with age, there is a fall in light transmission by the lens, associated with increased light scatter, increased spectral absorption, particularly at the blue end of the spectrum, and increased lens fluorescence. A major factor responsible for the increased yellowing of the lens is the accumulation of a novel fluorogen, glutathione-3-hydroxy kynurenine glycoside, which makes a major contribution to the increasing fluorescence of the lens nucleus which occurs with age. Since this compound may also cross-link with the lens crystallins, it may contribute to the formation of high-molecular-weight aggregates and the increases in light scattering which occur with age. Focal changes of microscopic size are observed in apparently transparent, aged lenses and may be regarded as precursors of cortical cataract formation.

System, apparatus, and method for correcting vision using an electro-active lens

Abstract: A spectacle lens is disclosed. The disclosed lens provides a vision correcting area for the correction of a wearer's refractive error. The viewing correction area provides correction for non-conventional refractive error to provide at least a part of the wearer's vision correction. The lens has a prescription based on a wave front analysis of the wearer's eye and the lens can further be modified to fit within an eyeglass frame.

Eyeglass display lens system employing off-axis optical design

Abstract: An off-axis optical display system is provided. The system comprises an eyeglass lens assembly having the first lens section (30) having a first surface (40), at least a portion of the first surface having a first curvature (25), and a second lens section (20) having a second surface (40), at least a portion of the second surface having a second curvature. The interface comprises an optical layer and conforms to the first curvature of the first surface and the second curvature of the second surface (25). An image source (50-52) is located off-axis with respect to the interface to transmit light along an optical path (10) that reflects off the optical reflective surface (25) of the interface toward an eye of a user. A portion of the optical path may be through air, and refraction is provided at the interface between air and the first lens (36). An aberration correction element is also provided (31-32).

Hubble Space Telescope observations of 10 two-image gravitational lenses

Abstract: We report on a program to obtain Hubble Space Telescope (HST) observations of galaxy-mass gravitational lens systems at optical and infrared wavelengths. Here we discuss the properties of 10 two-image gravitational lens systems (Q0142-100 = UM 673, B0218+357, SBS 0909+532, BRI 0952-0115, LBQS 1009-0252, Q1017-207 = J03.13, B1030+074, HE 1104-1805, Q1208+1011, and PKS 1830-211). We grouped these 10 systems because they have limited lens model constraints and often show poor contrast between the images and the lens galaxy. Of the 10 lens galaxies, seven are probably early-type galaxies, two are probably late-type galaxies (B0218+357 and PKS 1830-211), and one was not detected (Q1208+1011). We detect the host galaxies of the zs = 4.50 lensed quasar in BRI 0952-0115, the zs = 2.32 lensed quasar in HE 1104-1805, and the unlensed z = 1.63 quasar near LBQS 1009-0252. We fit a set of four standard lens models to each lens that had sufficient constraints to compare isothermal dark matter and constant mass-to-light lens models, and to explore the effects of local tidal shears.

Multiplexed fluorescent detection in microfluidic devices

Abstract: An optical detection and orientation device is provided comprising housing having an excitation light source. An optical element for reflecting the excitation light to an aspherical lens and transmitting light emitted by a fluorophore excited by said excitation light, a focusing lens for focusing the emitted light onto the entry of an optical fiber, which serves as a confocal aperture, and means for accurately moving said housing over a small area in relation to a channel in a microfluidic device. The optical detection and orientation device finds use in identifying the center of the channel and detecting fluorophores in the channel during operations involving fluorescent signals.

Spacetime perspective of Schwarzschild lensing

Abstract: (November 29, 1999)We propose a definition of an exact lens equation without reference to a background spacetime,and construct the exact lens equation explicitly in the case of Schwarzschild spacetime For theSchwarzschild case, we give exact expressions for the angular-diameter distance to the sources aswell as for the magnification factor and time of arrival of the images We compare the exactlens equation with the standard lens equation, derived under the thin-lens-weak-field assumption(where the light rays are geodesics of the background with sharp bending in the lens plane, andthe gravitational field is weak), and verify the fact that the standard weak-field thin-lens equationis inadequate at small impact parameter We show that the second-order correction to the weak-field thin-lens equation is inaccurate as well Finally, we compare the exact lens equation with therecently proposed strong-field thin-lens equation, obtained under the assumption of straight pathsbut without the small angle approximation, ie, with allowed large bending angles We show thatthe strong-field thin-lens equation is remarkably accurate, even for lightrays that take several turnsaround the lens before reaching the observerI INTRODUCTION

Apparatus for optical distancing autofocus and imaging and method of using the same

Abstract: An automatic distancing, focusing and optical imaging apparatus for optical imaging of an object is disclosed, having at least one lens, a distancing sensor adapted to receive light rays representative of the image that travel through the lens, an imaging sensor adapted to receive light rays representative of the image that travel through the lens, and at least one processor coupled to the distancing sensor and the imaging sensor, the processor for controlling the movement of the imaging sensor to a position for optimal imaging and for processing the image received by the imaging sensor.

Understanding the Microstructure and Properties of Components Fabricated by Laser Engineered Net Shaping (LENS)

Abstract: Laser Engineered Net Shaping (LENS) is a novel manufacturing process for fabricating metal parts directly from Computer Aided Design (CAD) solid models. The process is similar to rapid prototyping technologies in its approach to fabricate a solid component by layer additive methods. However, the LENS technology is unique in that fully dense metal components with material properties that are similar to that of wrought materials can be fabricated. The LENS process has the potential to dramatically reduce the time and cost required realizing functional metal parts. In addition, the process can fabricate complex internal features not possible using existing manufacturing processes. The real promise of the technology is the potential to manipulate the material fabrication and properties through precision deposition of the material, which includes thermal behavior control, layered or graded deposition of multi-materials, and process parameter selection. This paper describes the authors' research to understand solidification aspects, thermal behavior, and material properties for laser metal deposition technologies.

Image pickup lens device

Abstract: PROBLEM TO BE SOLVED: To provide an image pickup lens device equipped with a high variable power zoom lens system capable of making the reduction of cost compatible with compaction, having an F-value showing a bright condition and having the zoom ratio of about 3. SOLUTION: The zoom lens system is composed of a 1st negative lens group (Gr1), a 2nd positive lens group (Gr2) and a 3rd positive lens group (Gr3) in order from an object side and performs zooming by changing a distance between the respective lens groups. Each of the lens groups (Gr1 to Gr3) is composed of one lens, and the 1st and the 2nd lens groups (Gr1 and Gr2) are moved on an optical axis (AX) to perform zooming. It satisfies a conditional expression: 0.2

Method and apparatus for measurement of the refractive properties of the human eye

Abstract: A system, and its method, for measuring the optical properties of an eye employs optical components for detecting both the reflection of a first light beam from the anterior surface of the eye, and the reflection of a second light beam from the retina of the eye. Sensors are included to receive and separate each of these reflected light beams into a plurality of individual beams, each having its own specific optical path length. The optical path lengths of individual beams reflected from the cornea are collectively used to create a topographical map of the cornea's anterior surface and the optical path lengths of individual beams reflected from the retina are collectively used to create an acuity map of the entire eye. Further, there are additional optical components which respectively determine the position of the eye, a length for the eye and an aberration for the relaxed lens of the eye. A computer is then used to compare the topographical map with the acuity map, while compensating for the lens aberration, to construct a topography for the posterior surface of the cornea.

Defect inspection method and apparatus therefor

Abstract: A defect inspection apparatus for inspecting a fine circuit pattern with high resolution to detect a defective portion is constructed to have an objective lens for detecting an image of a sample, a laser illumination unit for illuminating the sample through the objective lens, a unit for reducing the coherence of the laser illumination, an accumulation type detector, and a unit for processing the detected image signal.

Principles of parametric temporal imaging. I. System configurations

Abstract: The recently developed process of temporal imaging expands or compresses time waveforms while preserving the shapes of their envelope profiles. A key element in a temporal imaging system is a time lens which imparts a quadratic phase modulation to the waveform being imaged. Several methods, such as electrooptic modulation, can be used to produce the phase modulation. In this paper, we concentrate on the parametric mixing of a signal waveform with a linearly chirped optical pump as the time lens mechanism. We analyze all single-lens system configurations including sum- and difference-frequency mixing schemes with positive and negative group velocity dispersions using temporal ray diagrams as an aid in understanding their operation.

Principles of Hartmann-Shack aberrometry.

Abstract: RAY OPTICS DESCRIPTION Nearly 400 years ago, the celebrated Jesuit philosopher-astronomer, Christopher Scheiner, professor at the University of Ingolstadt, demonstrated the focusing ability of the human eye using a simple device known as the Scheiner Disk.1 Scheiner's experiments showed that if an optically imperfect eye views through an opaque disk perforated with two pinholes, a single distant point of light such as a star will form two retinal images as illustrated in Figure 1. If the eye's optical imperfection is a simple case of defocus, then the double retinal images can be brought into register by viewing through a spectacle lens of the appropriate power. For optical aberrations other than defocus, however, a simple lens won't bring the two retinal images into coincidence. In such cases a more general method is needed for quantifying the refractive imperfections of the eye at each pupil location. This is achieved by using a fixed light source for the central, reference pinhole and a moveable light source for the outer pinhole as illustrated in Figure 2. By adjusting the moveable source horizontally and vertically, the isolated ray of light is redirected until it intersects the fixed ray at the retina and the patient now reports seeing a single point of light. Having made this adjustment, the displacement distances x and y are measures of the ray aberration of the eye at the given pupil point. This subjective aberrometer was first described by Smirnov2 and has been used extensively in visual optics research the past 40 years. To convert the Scheiner-Smirnov subjective technique into an objective aberrometer, we reverse the direction of light propagation by placing a spot of light on the retina. This spot then becomes a point source which radiates light back out of the eye as illustrated in Figure 3. Additional holes are drilled in Scheiner's disk, which astronomers and optical designers call a Hartmann screen.3 Each aperture in the Hartmann screen isolates a narrow pencil of rays emerging from the eye through a different part of the pupil. These emerging rays intersect a video Principles of Hartmann-Shack Aberrometry

Focusing cold neutrons with multiple biconcave lenses for small‐angle neutron scattering

Abstract: The focusing of a cold neutron beam by multiple biconcave lenses has recently been proposed as a practical means of extending the lower limit of Q in conventional, long flight-path small-angle neutron scattering (SANS) instruments. To test the feasibility of this approach, we have carried out extensive measurements on one of the 30 m SANS instruments at NIST of the focusing characteristics of a set of 28 biconcave MgF2 lenses. The focused beam profile has been measured over several orders of magnitude using high resolution neutron auto-radiography. The focusing lens configuration outperforms the pinhole collimation at Qmin lower than 0.004 A-1. At Qmin = 0.001 A-1, the intensity gain of the lens configuration over the pinhole collimation is greater than one order of magnitude.

System and method of integrating corneal topographic data and ocular wavefront data with primary ametropia measurements to create a soft contact lens

Abstract: A system and method is provided for integrating corneal topographic data and ocular wavefront data with primary ametropia measurements to create a soft contact lens design. Corneal topographic data is used to design a better fitting soft contact lens by achieving a contact lens back surface which is uniquely matched to a particular corneal topography, or which is an averaged shape based on the particular corneal topography. In the case of a uniquely matched contact lens back surface, the unique back surface design also corrects for the primary and higher order optical aberrations of the cornea. Additionally, ocular wavefront analysis is used to determine the total optical aberration present in the eye. The total optical aberration, less any corneal optical aberration corrected utilizing the contact lens back surface, is corrected via the contact lens front surface design. The contact lens front surface is further designed to take into account the conventional refractive prescription elements required for a particular eye. As a result, the lens produced exhibits an improved custom fit, optimal refractive error correction and vision.

Eyewear heart rate monitor

Abstract: A heart rate monitor adapted to be worn on eyewear such as a pair of eyeglasses, a mask or goggles. The heart rate monitor includes a sensor in contact with the bridge of the user's nose. The sensor is responsive to pressure variations or pulses produced during a heart beat cycle. The sensor provides an analog signal having a frequency equal to the user's pulse rate. The analog signal output from the sensor provides an input signal for a microprocessor which includes a frequency counter and signal averager. A microprocessor output signal having a magnitude which is proportional to the heart rate in beats per minute provides the input signal for an optical readout device such as a digital display which is preferably mounted on the frame or stem of the user's eyewear. The image on the optical display is conducted to an eyepiece lens which is mounted most preferably on one of the lenses of the eyewear by means of an image conduit such as a fiber optic or fiber optic bundle. The eyepiece lens is positioned such that the image of the optical display is positioned at the focal plane of the user's eye for comfortable viewing. In a most preferred embodiment of the heart rate monitor, the microprocessor, power supply and digital display are contained within a housing that is releasably attached to eyewear. The proximal end of a fiber optic bundle is adjustably attached to the housing and in optical communication with the digital display. A display lens is adjustably attached to the opposing distal end of the fiber optic bundle. A pair of pulse rate sensor electrodes in contact with a user's nose provide an electrical signal containing pulse rate data to the microprocessor. The image on the digital display is conducted by the fiber optic bundle to the display lens adjustably disposed within the field of view of the user.

Optical lens system with electro-active lens having alterably different focal lengths

Abstract: An optical lens system that may include a lens with a first focal length and an electro-active region coupled to the lens, where activating the electro-active region alters a portion of the system to a second focal length such that the system has two different focal lengths.

Compensation of lens aberrations in digital holography.

Abstract: The possibility of compensating for the aberrations of an imaging lens in digital holography is outlined theoretically. The principle is demonstrated with a Mach–Zehnder arrangement and transilluminated objects. Diffraction-limited resolution can be obtained with a plano–convex lens. Amplitude and phase objects were imaged.

Camera control system

Abstract: PROBLEM TO BE SOLVED: To provide a camera control system, where a desired object to be watched can quickly and easily be designated and a camera motion can quickly be finished by avoiding an overshoot of the camera operation caused by a transfer delay specific to a system main body. SOLUTION: This camera control system allows a universal head controller 4 for controlling a universal head 2, so that the universal head is turned to an object angle after a universal head control signal outputted from a computer 7 is given to the universal head controller 4 and allows a lens controller 3 to regulate a lens 1a independently, after a lens control signal outputted from the computer 7 is given to the lens controller 3.

System and method for increasing the depth of focus of the human eye

Abstract: A method and apparatus for increasing the depth of focus of the human eye is comprised of a lens body, an optic in the lens body configured to produce light interference, and a pinhole-like optical aperture substantially in the center of the optic. The optic may be configured to produce light scattering or composed of a light reflective material. Alternatively, the optic may increase the depth of focus via a combination of light interference, light scattering, light reflection and/or light absorption. The optic may also be configured as a series of concentric circles, a weave, a pattern of particles, or a pattern of curvatures. One method involves screening a patient for an ophthalmic lens using a pinhole screening device in the lens to increase the patient's depth of focus. Another method comprises surgically implanting a mask in the patient's eye to increase the depth of focus.

Interlenticular opacification: clinicopathological correlation of a complication of posterior chamber piggyback intraocular lenses.

Abstract: Purpose To present a clinicopathological correlation of 2 pairs of piggyback posterior chamber intraocular lenses (PC IOLs) explanted because of opacification between the lens optics. Setting Gayton Health Center, Eyesight Associates of Middle Georgia, Warner Robins, Georgia, and Center for Research on Ocular Therapeutics and Biodevices, Storm Eye Institute, Medical University of South Carolina, Charleston, South Carolina, USA. Methods Two pairs of piggyback AcrySof® lenses were explanted from 2 patients with significant visual loss related to opacification between the optics. They were submitted for pathological analysis. Gross and histopathological examinations were performed, and photomicroscopy was used to document the results. Results Gross examination showed accumulation of a membrane-like white material between the lenses. Histopathological examination revealed that the tissue consisted of retained/proliferative lens epithelial cells (bladder cells or pearls) mixed with lens cortical material. Conclusion Piggyback PC IOLs were explanted in 2 cases because of a newly described complication, interlenticular opacification. Three surgical means may help prevent this complication: meticulous cortical cleanup, especially in the equatorial region; creation of a relatively large continuous curvilinear capsulorhexis to sequester retained cells peripheral to the IOL optic within the equatorial fornix; insertion of the posterior IOL in the capsular bag and the anterior IOL in the ciliary sulcus to isolate retained cells from the interlenticular space.

Molded image sensor package having lens holder

Abstract: An image sensor package (1100) includes an image sensor (106), a window (122), and a molding (124C), where molding (124C) includes a lens holder extension portion (1102) extending upwards from window (122). Lens holder extension portion (1102) includes a female threaded aperture (1106) extending from window (122) such that window (122) is exposed through aperture (1106). A lens (1210) is supported in a threaded lens support (1112). Lens support (1112) is threaded into aperture (1106) of lens holder extension portion (1102). Lens (1210) is readily adjusted relative to image sensor (106) by rotating lens support (1112).

Nanofabrication and diffractive optics for high-resolution x-ray applications

Abstract: Short wavelength x-ray radiation microscopy is well suited for a number of material and life science studies. The x-ray microscope (XM1) at the Advanced Light Source Synchrotron in Berkeley, California uses two diffractive Fresnel zone plate lenses. The first is a large condenser lens, which collects soft x-ray radiation from a bending magnet, focuses it, and serves as a linear monochromator. The second is the objective zone plate lens, which magnifies the image of the specimen onto a high-efficiency charge coupled device detector. The objective lens determines the numerical aperture and ultimate resolution. New objective lens zone plates with a minimum linewidth of 25 nm and excellent linewidth control have been fabricated using Berkeley Lab’s 100 keV Nanowriter electron beam lithography tool, a calixarene high-resolution negative resist, and gold electroplating. Although the condenser zone plate is less critical to the resolution of the instrument, its efficiency determines the flux on the sample and ul...

Light emitting diode linear array with lens stripe for illuminated signs

Abstract: A linear array of light emitting diodes with a lens stripe for evenly illuminating signs, which includes a linear array of light emitting diodes (LEDs) for producing a light output, and an elongated lens stripe. The linear array of LEDs includes an elongated mounting member and a plurality of LEDs mounted along the length of the mounting member. The elongated lens stripe is attached to the linear array of LEDs, and includes a reflector portion and a lens portion. The reflector portion has two elongated and opposing side walls that form an elongated channel. The side walls are light reflective. The LEDs are disposed inside the channel. The channel side walls reflect the light output from the LEDs toward the elongated open end of the channel. The lens portion has an elongated lens disposed along the open end of the channel for focusing the light output from the LEDs. The focused light output enters the side edge of a display board type sign for even illumination, or is projected onto the opaque front surface of a sign for even illumination.

X-ray refractive planar lens with minimized absorption

Abstract: Silicon refractive planar parabolic lenses with minimized absorption were fabricated by a combination of photolithography and dry-etching techniques. Focusing and spectral properties of the lenses were studied with synchrotron radiation in the energy range 8–25 keV at the European Synchrotron Radiation Facility. A focal spot of 1.8 μm with a gain of 18.5 and transmission of more then 80% was measured at 15.6 keV. The spectral characteristics were analyzed taking into account material dispersion and photon-energy attenuation in the hard x-ray range.

Multifocal ophthalmic lens with reduced halo size

Abstract: Ophthalmic lenses, for example, intraocular lenses, contact lenses, corneal implant lenses and the like, have multifocal characteristics which provide beneficial reductions in at least the perception of one or more night time visual symptoms such as “halos”, and “glare or flare”.